Fuse-plug



R. S. PORTER.

FUSE PLUG.

APPLICATION FILED MAY I5. 1918.

1,372,450. Patented Mar. 22, 1921.

o a? o I INVENTOR P01426? WITNESSES ATTORNEY ROBERT S. PORTER, OF SAN DIEGO, CALIFORNIA,

ASSIGNOR 0F ONE-HALF TO DONALD C. BURNI-IAM, 0F SAN DIEGO, CALIFORNIA.

FUSE-PLUG.

Application filed May 15, 1918.

'[0 all whom t mar/y concern.'

Be it known that I ROBERTS. PORTER, a citizen of the United tates, residing at San Diego, in the county of San Diego and State of California, haveinvented a new and useful F use-Plug, of which the following is a specification.

This invention has reference to fuse plugs for electric circuits, and its object is to provide a plug in which the fuse may be renewed at will without the aid of tools and which will clearly indicate the fact that the fuse has blown if such be the case. The ready renewability of the fuse permits the conserving of expensive metal, of which part of the fuse structure is made, since the usual -fuse plugs are of a character necessitating the throwing away of such fuse plugs when once blown.

The invention comprises a fuse plug which, in general appearance', may simulate the ordinary fuse plug but the fusible strip is carried by a uickly removable cartridge requiring no too s for its removal and permitting the insertion of another fuse Wire or strip also without the aid of tools, whereby anyone may quickly restore the fuse plug to its original worln'ng condition in the event of a blow-out, beside being able to locate the blown fuse without difficulty, the identification of a blown fuse being one of considerable difficulty with the ordinary commercial fuse plug. The removable member or cartridge is arranged to hold the fusible wire or strip in place under tension so that in the event of 'a blow-out a portion of the holding means will be propelled within the fuse plug to a point where it will be readily visible but still wholly inclosed in the plug against any possibility of the scattering of hot metal or the production of an arc where the flame would reach the outside of the fuse the cartridge may be slipped into and out of place without any positive holding means requiring extra manipulation and when the fuse is blown the cartridge is readily dismantled, since the elements will slip apart without effort or the use of tools.

` The invention will be best understood from a consideration of the following detailed description taken in connection with the accompanying drawing forming part of this specification, with the understanding, however, that theinvention is not confined Specification o f Letters Patent.

plug. The arrangement is such Patented Mar. 22, 1921. serial No. 234,736. 4

to any strict. conformity with the showiiw of the drawing but may be changed and modified so long as such changes and modino material departure from the salient features of the invention as expressed in the appended claims.

In the drawing I Figure l is a longitudinal diametric section of a fuse plug, embodying the invention, on an enlarged scale.

Fig. 2 is an inverted plan view of the plug show n in Fig. 1.

F ig. 3 is an elevation of the cartridge, omitting the fusible member and viewed from the right hand side of Fig. 1.

Fig. 4 is an elevation of a fusible member adapted to the fuse plug but separate there- Fig. 5 is a longitudinal diametric section of a modified form of part of the fuse plug cartridge.

Fig. 6 is a plan view thereof.

eferring to the drawing, there is shown a body member l of a shape corresponding to the usual screw fuse plugs of commerce and may be conveniently made of porcelain, the body member l having the usual exterior screw shell near one end and a metal sleeve 3 constituting a cap for retainingl a mica cover 4 for a cavity or chamber 5 within the body l, this cavity opening through the screw end of the plug by way of a passage 6.

Adapted to the interior of the body 1 is a cartridge comprising a sleeve 7 of insulating material, such as vulcanized fiber or any other suitable material, and this sleeve in the showing of Fig. 1 has one end 8 slightly tapered on the exterior, the taper being somewhat exaggerated in Fig. 1. Fitted closely yet freely to the taper end 8 is a taper cap or thimble 9 having its smaller end formed into an inturned fiange 10 overriding the extremity of the taper end 8. This cap is held in place by a pin 11 fast to the sleeve 7 and fitting a bayonet slot l2 in the thimble. The flange 10 defines a passage 13 through which there extends a sleeve 14 having at one end an outturned flange 15 having a spread sufficient to engage the inturned flange 10 and so serve as a stop to prevent movement of the sleeve 14 in one direction through the passage 13. The sleeve 14 at an appropriate distance from the flange 15 is expanded, as shown at 16, to form a shoulder. Lodge'd between the Hange 10 and shoulder 16 and surrounding the sleeve 14 is a spring 17 tending to move the fiange 15 into engagement with the Hange 10. Projecting from the end of the sleeve 14 provided with the shoulder 16 are opposed ears 18 on opposite sides of thel sleeve and these ears are each provided with a perforation 19.

Fitted tightly to that end of the sleeve 7 remote from the taper end thereof is a thim ble 20 having a closure 21 at one end extend ing beyond the margins of the thimble and constituting a contact lfor the fuse The thimble 20 is crimped or otherwise m c securely fast to the sleeve 7 but fits loosely in the passage 6, the looseness of fit being exaggerated in Fig. 1 to indicate that the thimble and the parts to which it 1s fast may be readily removedfrom the body of the plug, no part of which plug -1s of greater diameter than the opening or passage 6.

.Fast to the screw shell 2, by solder 22 or otherwise, are springs 23 each extending through a suitable passage 24 through the corresponding side of the body member 1.

These springs 23 are so shaped as to bearl against the thimble 9 when the cartridge is properly located within the body` l of the plug, the engagement being sufficiently strong to make good electrical contact.

There is also provided a strip or wire 25l of fusible metal, such as is customarily employed in fuse plugs, and this strip has a head 26 at one end, the head being shaped to fit a countersunk or taper passage v27 through the member 21 of the thimble 20.

When the parts are assembled the strip 25 is inserted through the passa-ge4 27 until the head 26 engages in the passage and the other end of the strip is threaded through the sleeve 14 and through one perforation 19 in one ear 18, thence to the other ear 18 and through the perforation 19 therein and folded down against the inside ofthe ear in a manner to secure or lock the strip against pulling out, the sleeve 14 being pressed toward the thimble 20 to compress the spring 17, wherefore, the fusible strip 25 is under tension and the ears 18 are spaced away from the mica plate4.

When the cartridge is inserted the springs 23 hold it against accidental displacement and, of course, when the fuse plug is screwed into place in the usual manner the parts are all held securely in the operative position.

When the strip 25 blows the cartridge remains in its proper position but the strip 25 no longer `holding the sleeve 14 retracted,

releases the sleeve to the action of the spring 17 and the sleeve is forced toward the mica cover or plate 4 until in close relation thereto and therefore clearly visible through the mica plate 4, so that there is' no difiiculty whatever in identifying a blown fuse even when the mica cover is of dark tint as fre quently occurs with the mica used in fuse plugs.

When a fuse is blown the plug is removed from the -socket in which it is located and the fuse cartridge is pulled out ofthe plug, this being easily accomplished because of the loose'it of the thimble 20 and the fact thatthe cartridge is held in place solely by the` fuse.

Instead of the sleeve 14 with the axially extended ears 18, there` may be provided a sleeve 14a with ears 18 in radial relation to the longitudinal axis of the sleeve, as indicated in Figs. 5 and 6, the general a rangement being the same .as shown in igs. 1 and 3, but -permitt-ing a greater travel of the sleeve and the shortening of the length of the plug as a whole. The head end 21 of the thimble 20 may have the passage 27 of a size. permitting only a certain size of fuse and the head 21'may be .stamped with a num- 'ber denoting the rating of the fuse sothat the cartridge may not be charged with a large fuse than the rating.

The shell 2 hasbeen described as a threadvthimble constituting a Contact .base for the plug and to which thimble one end of the sleeve is fast, another thimble at and made fast to the other end of the sleeve, another sleeve movable lengthwise of the first named sleeve at one end of the latter and having a limited movement in the second named thimble away from the base of the plug, and the second named sleeve extending through and beyond the second named thimble at the end remote from the base of the plug, and a -spring carried by the second named sleeve and tending to move said sleeve.

2. In a fuse 4plug provided with a body member, a removable fuse 'cartridge for insertion in the body member, said cartridge comprlsing an insulating sleeve, -a thimble vconstituting a Contact base for theiplug and to which thimble one end of the sleeve is fast, another thimble at and made fast to the'other end of the sleeve, another sleeve movable lengthwise of the first named sleeve at one end of the latter and having alimited movement in the second named sleeve away from the base of the plug, and the second named sleeve extending through and beyond the second named thimble at the end remote from the base of the plug, a spring carried by the second named sleeve and tending to move said second named sleeve in a direction away from the base ofithe plug, said second named sleeve having portions projecting therefrom for the attachment of a fusible strip, and spring contacts on the body member in position to engage the second named thimble. of the fuse cartridge to hold the latter in the inserted position.

3. A fuse plug including ,an insertible and removable fuse cartridge comprising a sleeve of insulating material, conducting members at opposite ends of the sleeve and electrically separated thereby,an0ther sleeve mounted in and movable along one of the conducting members and provided with a spring tending to maintain the second named sleeve at one limit of its travel, said sleeve having perforated ears at one end and the conducting member distant from that carrying the second named sleeve having a perforation therethrough, and a fusible element With a head at one end for` lodgment in the perforation in the second named conducting member and of a length to be threaded through the second named sleeve and through the perforated ears at one end of said second named sleeve, With said second named sleeve held toward the other limit of its movement by the fusible element With the spring compressed.

In testimony that I claim the foregoing as my own, I have hereto aixed my signature.

ROBERT S. PORTER.

Witnesses:

A. A. MURPHY, LEE J. E. WILSON. 

